// tutorial02.c
// A pedagogical video player that will stream through every video frame as fast as it can.
//
// This tutorial was written by Stephen Dranger (dranger@gmail.com).
//
// Code based on FFplay, Copyright (c) 2003 Fabrice Bellard, 
// and a tutorial by Martin Bohme (boehme@inb.uni-luebeckREMOVETHIS.de)
// Tested on Gentoo, CVS version 5/01/07 compiled with GCC 4.1.1
//
// Updates tested on:
// Mac OS X 10.11.6
// Apple LLVM version 8.0.0 (clang-800.0.38)
//
// Use 
//
// $ gcc -o tutorial02 tutorial02.c -lavutil -lavformat -lavcodec -lswscale -lz -lm `sdl-config --cflags --libs`
//
// to build (assuming libavutil/libavformat/libavcodec/libswscale are correctly installed your system).
//
// Run using
//
// $ tutorial02 myvideofile.mpg
//
// to play the video stream on your screen.


#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>

#include <SDL.h>
#include <SDL_thread.h>

#ifdef __MINGW32__
#undef main // Prevents SDL from overriding main().
#endif

#include <stdio.h>

int main(int argc, char *argv[]) {
	AVFormatContext *pFormatCtx = NULL;
 	int i, videoStream;
 	AVCodecContext *pCodecCtx = NULL;
 	AVCodec *pCodec = NULL;
 	AVFrame *pFrame = NULL; 
 	AVPacket packet;
 	int frameFinished;
 	//float aspect_ratio;	
 	AVDictionary *optionsDict = NULL;
 	struct SwsContext *sws_ctx = NULL;	

 	SDL_Surface *screen = NULL;
 	SDL_Overlay *bmp = NULL;
 	SDL_Rect rect;
 	SDL_Event event;

	if (argc < 2) {
		fprintf(stderr, "Usage: test <file>\n");
		exit(1);
	}
	// Register all formats and codecs.
	av_register_all();
  
	if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
		fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
		exit(1);
	}

	// Open video file.
	if (avformat_open_input(&pFormatCtx, argv[1], NULL, NULL) != 0) {
		return -1; // Couldn't open file.
	}
  
	// Retrieve stream information.
	if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
		return -1; // Couldn't find stream information.
	}
  
	// Dump information about file onto standard error.
	av_dump_format(pFormatCtx, 0, argv[1], 0);
  
	// Find the first video stream.
	videoStream = -1;
	for(i = 0; i < pFormatCtx->nb_streams; i++) {
		if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
			videoStream = i;
			break;
		}
	}
	if (videoStream == -1) {
		return -1; // Didn't find a video stream.
	}
  
	// Get a pointer to the codec context for the video stream.
	pCodecCtx = pFormatCtx->streams[videoStream]->codec;

	// Find the decoder for the video stream.
	pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
	if (pCodec == NULL) {
		fprintf(stderr, "Unsupported codec!\n");
		return -1; // Codec not found.
	}

	// Open codec
	if (avcodec_open2(pCodecCtx, pCodec, &optionsDict) < 0) {
		return -1; // Could not open codec.
	}

	// Allocate video frame.
	pFrame = av_frame_alloc();

	// Make a screen to put our video.
#ifndef __DARWIN__
	screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 0, 0);
#else
	screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 24, 0);
#endif
	if (!screen) {
		fprintf(stderr, "SDL: could not set video mode - exiting\n");
		exit(1);
	}
  
	// Allocate a place to put our YUV image on that screen.
	bmp = SDL_CreateYUVOverlay(pCodecCtx->width, pCodecCtx->height, SDL_YV12_OVERLAY, screen);
  
	sws_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BILINEAR, NULL, NULL, NULL);

	// Read frames and save first five frames to disk.
	i = 0;
	while(av_read_frame(pFormatCtx, &packet) >= 0) {
		// Is this a packet from the video stream?.
		if (packet.stream_index == videoStream) {
			// Decode video frame.
			avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);

			// Did we get a video frame?
			if (frameFinished) {
				SDL_LockYUVOverlay(bmp);

				AVFrame pict;
				pict.data[0] = bmp->pixels[0];
				pict.data[1] = bmp->pixels[2];
				pict.data[2] = bmp->pixels[1];

				pict.linesize[0] = bmp->pitches[0];
				pict.linesize[1] = bmp->pitches[2];
				pict.linesize[2] = bmp->pitches[1];

				// Convert the image into YUV format that SDL uses.
				sws_scale(sws_ctx, (uint8_t const * const *)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pict.data, pict.linesize);

				SDL_UnlockYUVOverlay(bmp);

				rect.x = 0;
				rect.y = 0;
				rect.w = pCodecCtx->width;
				rect.h = pCodecCtx->height;
				SDL_DisplayYUVOverlay(bmp, &rect);

			}
		}
    
		// Free the packet that was allocated by av_read_frame.
		av_packet_unref(&packet);
		
		SDL_PollEvent(&event);
		switch (event.type) {
			case SDL_QUIT:
				printf("SDL_QUIT\n");
				SDL_Quit();
				exit(0);
				break;
			default:
				break;
		}

	}
  
	// Free the YUV frame.
	av_free(pFrame);

	// Close the codec.
	avcodec_close(pCodecCtx);

	// Close the video file.
	avformat_close_input(&pFormatCtx);

	return 0;
}
